Previous studies show that the administration of procaine to bipolar and borderline patients gives rise to a diversity of behavioral responses ranging from euphoria to dysphoria. Since procaine is believed to selectively stimulate the limbic structures of the brain, it is reasoned that these behavioral differences might result from neuroclinical differences in these regions of the brain. Given that alcohol might alter limbic structures, we administered procaine to alcoholics, subjects with panic disorder, panic subjects with alcoholism and controls. Preliminary analyses of our results show alcoholics with panic disorder were more likely to experience a panic attack following procaine than were alcoholics without panic disorder or controls. Similarly, alcoholics with panic disorder had a greater rise in pulse per unit change in vagal tone compared to these other groups. Presently, there is insufficient data concerning panic subjects without alcoholism to draw any conclusion about this subgroup.